How An Allergist Diagnoses Allergies

If you have never been diagnosed with allergies but think you might have them or aren't sure what causes your allergy symptoms, see an allergist.

When you visit, the doctor will:

Take a medical history. You will be asked about your health, your symptoms and whether members of your family have asthma or allergies such as hay fever, hives or skin rashes like eczema.

Ask you about your symptoms. The doctor will want to know when symptoms occur, how often they happen and what seems to bring them on. The allergist will also ask about your work, home and eating habits to see if these can provide clues to help pinpoint your allergy.

Do a physical exam.

Conduct allergy tests.

Tests can be done for common allergens such as plant pollens, molds, dust mites, animal dander, insect stings and various foods such as peanuts, eggs, wheat, shellfish and milk. Testing also is available for some medicines, such as penicillin. There are two types of skin tests:

The prick test pricks the surface of the skin with a tiny amount of the allergen. The test is done on your back or the inside of your arms with several allergens tested at once. If you're allergic, redness and swelling appear at the site of the prick.

The intradermal test injects the allergen with a very fine needle under the first few layers of the skin. This type of skin test may be used when the result of a prick test is not clear.

Allergy Blood Tests

Skin tests are more sensitive than blood tests, but a blood test to help diagnose allergies if:

You're taking a medicine that could interfere with allergy test results.

You have very sensitive skin or a serious skin condition.

You had a previous reaction to an allergen that suggested you were very sensitive and should avoid more exposure.

After drawing blood, the sample is sent to a lab to look for the antibodies of specific allergens that show if you have allergies. It takes a few days to receive blood test results.